Exhaust systems of modern internal combustion engines, such as, for example, those for motor vehicles, may be regularly provided with catalytic converters for converting harmful exhaust gases into harmless reaction products. In order for the catalytic converters to function well, it may be required to feed air and fuel to the engine in a predefined proportion. The engine controls provided for this purpose may be connected on their input side to a so-called lambda probe whose signals represent the composition of the exhaust gas and thus may enable the engine control to adjust the ratio of fuel and combustion air in a manner optimal for the catalytic converter.
Modern heating devices in which fuels are burned to generate heat may work similarly.
The sealing packing mentioned in the introduction may have a plurality of functions. For example, in the housing of the sensor body, it may separate a measuring gas chamber or an exhaust-gas chamber from a reference-gas chamber. Additionally, it may also support the sensor body in the housing, whose inner cross-section may have a shape that deviates from the outer cross-section of the sensor body. Furthermore, the sealing packing may keep the sensor body electrically potential-free, or may insulate it electrically from the housing, which may be made of metal.
The sealing packing may be built up from a plurality of layers, the different layers assuming various main functions, such as protecting the remaining layers from pulsations of the exhaust gas, firmly supporting the sensor body in the housing, and sealingly separating the exhaust-gas chamber and the reference-gas chamber from one another.
A steatite-pressure packing into which a boron nitride disk is inserted may provide the sealing separation of the measuring gas chamber or exhaust gas chamber and the reference gas chamber with respect to one another. This may ensure good electric insulation between the sensor body and the associated housing and good sealing from gasoline vapors or fuel vapors as well as liquid fuel.
However, the required manufacturing effort may be relatively high.